FIELD OF THE INVENTION
The invention relates to a drive device for a front-loading washing machine having a laundry drum which is supported overhung by an at least substantially horizontal shaft within a bearing sleeve of a stiff carrier part mounted at a rear-wall of a washing liquid container, which is driven directly by a flat motor that is likewise mounted at the rear wall of the washing liquid container.
Such drive devices are known from German Published, Non-Prosecuted Patent Applications DE 39 27 426 A1 and the DE 43 41 832 A1. In those devices, the stator of the motor which is constructed as a collectorless external rotor direct current motor, is fastened directly on the bearing sleeve of the stiff carrier part. The shaft is supported in the bearing sleeve and connected at its outer end with the rotor of the motor so as to be secure against rotation. The rotor therein is a so-called external rotor which engages over the stator windings like a pot and carries poles constructed as permanent magnets. In automatic washing machines according to German Published, Non-Prosecuted Patent Application DE 43 41 832 A1, the motor is additionally surrounded by an insulating rod which attenuates noises radiated directly from the motor to the surrounding atmosphere.
In the known drive devices, the stator is exposed to an appreciable temperature loading in its windings due to heat flow. The stator is encapsulated by a rotor having a pot-shaped structure (and additionally by a sound-insulating hood in the case of German Published, Non-Prosecuted Patent Application DE 43 41 832 A1) so strongly that cooling of the motor does not take place at all. That is also enhanced above all by a direct driving motor of the type that is hardly able to reach self-cooling by virtue of the self-rotating rotor, because of its necessarily low inherent rpm. Therefore, the known drive devices are practically only usable when they are protected against rapid overheating by external cooling.
Beyond that, the known drive devices cannot be delivered to the washing machine manufacturing plant as an already assembled motor. The stators and rotors thereof must be delivered separately and only be assembled with each other in the washing machine plant. Since special assembly equipment for the completion of motor assemblies as a rule is not present in a washing machine plant and is also not desired, the completion of the stator assembly to be connected with the liquid container system by the external rotor assembly as a rule can only take place inaccurately. Since extremely high demands are made on the maintenance of a small air gap, which as far as possible is always equally great for each product, wherein the air gap is between the stator poles and the rotor poles as well as on the centered bearing, and those demands are not to be fulfilled in the aforementioned assembly in a washing machine factory, the known drive devices are practically only very conditionally usable.